SOVIET COMMERCIAL SPACE BID SUFFERS IN NEW ROCKET FAILURE

By JOHN NOBLE WILFORD

Published: May 1, 1987

Soviet efforts to enter the commercial space transportation business suffered another setback last week with the second failure in three months involving the Proton rocket, American space experts reported yesterday.

A four-stage Proton rocket, launched April 24, failed to deliver its payload of three navigation satellites to the desired high orbit, apparently because of a malfunction of the fourth-stage propulsion system. The Soviet Union has not acknowledged the malfunction in news accounts.

A seemingly similar failure marred a Proton mission last January. According to American observers, Soviet officials attributed that failure to the improper performance of the payload, not the Proton itself. One American analyst called the explanation ''improbable.'' In any event, the results were much the same, with the payload, a communications satellite, left in a low and useless orbit.

James E. Oberg, a Houston engineer who is an authority on the Soviet space program, said in a telephone interview that tracking data of the April 24 launching showed there was ''clearly a failure in the last stage of the booster.'' Engine Cut Off Prematurely

After the Proton's first three stages fired successively to reach a 124-mile-high orbit, Mr. Oberg said, the fourth and uppermost rocket engine ignited but then cut off prematurely. Instead of being boosted to a circular orbit 12,000 miles above the Earth, the three navigation satellites were sent no higher than a sharply elliptical orbit ranging from 132 miles to 11,000 miles.

A day later the official Soviet press agency, Tass, made a cryptic announcement saying that the three satellites, designated Cosmos 1838, 1839 and 1840, were in orbit with ''scientific apparatus for space research.''

The apparatus was reported to be functioning ''normally,'' which Mr. Oberg said was ''probably literally true but not the whole truth.'' He said the navigation satellites, part of a new Soviet worldwide network, were of little value in their present orbit.

Soviet space officials opened a drive last year to attract foreign customers for the Proton rockets. At least one satellite launching for India has been signed up. But an analysis in the 1986 issue of ''The Soviet Year in Space,'' prepared by Nicholas L. Johnson, a Soviet expert with the Teledyne Brown Engineering Company, found a ''credibility gap with the vehicle'' and a feeling among prospective customers that ''the Soviets were not being completely honest'' about the Proton's record.

With a 93 percent success rate since their introduction in 1965, according to this analysis, the powerful four-stage versions of the Protons have been the most dependable launching system for heavy payloads and missions to space used by the Russians. The fourth-stage engine implicated in recent failures operates on kerosene and liquid oxygen and represents a relatively old-fashioned technology.